Here is the full list of all 22 Piko Piko achievements.
Run or you're gonna be late!
Beat Cookiebius
Defeat π-ko
Defeat Tanker Girl
Get to Level 10
Get to Level 20
Get to Level 50
Defeat Fruggles
Help the Bike Girl
Defeat a Bomb Cat with their own Bomb.
Mess up Nyan's house
Join up with your floof fox friend Nyan!
Knock the Hammer Cat's hammer back at em!z
"Attempt" to rescue the balloon.
Swoooooooosh!
I don't think this is the School path...
Get in the school without Nyan in your team.
Get in the Neon Fusion blaster
Finish the game.
Defeat the hidden witch boss
Get 999g